This invention relates to coronary angioplasty and, more particularly, to a plaque-coring catheter assembly for removing plaque from coronary arteries.
A technique for coronary angioplasty has been developed which generally involves the use of a catheter system including a dilation catheter which is introduced, for example, via the femoral artery and advanced to the site of a stenotic lesion in a coronary artery. An extensible balloon mounted on the distal end of the dilation catheter is then inflated with a fluid. As the balloon is inflated, atherosclerotic material disposed on the vessel wall is compressed in a direction generally perpendicular to the wall of the vessel. This dilates the vessel to facilitate blood flow therethrough. While this technique has been rather successful in a number of instances, restenosis is common and, in the event the plaque cracks during expansion, subsequent collapse of the coronary artery is likely.
It would therefore be desirable to minimize the likelihood of restenosis of the vessel by removing at least a portion of the atherosclerotic plaque from the vessel rather than merely compressing the plaque. One manner in which the foregoing can be achieved is by guiding an catheter through the vascular system to the locus of a stenotic lesion and mechanically cutting the plaque from the vessel wall. Of course, once the plaque has been severed from the vessel wall, a means must be provided for removing the plaque from the vessel. This can be achieved, for example, by the provision of suction and lavage lumens in the catheter or by providing some structure to receive the severed plaque and carry same during removal of the catheter from the patient.
One such "atherectomy" catheter has been proposed and is currently under investigational use. This catheter is known as the Peripheral Simpson Atherectomy Catheter (P-SAC) manufactured by Devices for Vascular Intervention, Inc. (DVI). The P-SAC is designed to excise atheromatous material from diseased peripheral vessels after it has been percutaneously or intraoperatively introduced and directed to a target stenotic lesion by means of guide wire assisted navigation techniques. This catheter has several lumens and is equipped distally with a cylindrical cutter enclosed within a housing assembly. A balloon is positioned opposite an opening defined in the housing and is adapted upon inflation to urge the opening of the housing/cutter assembly against a target portion of atherosclerotic plaque. The cutter is then activated and is slowly advanced to excise the portion of the plaque extending through the opening into the housing interior. The cutter is designed to travel along the entire length of the housing and trap the excised material within the distal end of the housing. Upon completion of the cut, the balloon is deflated and the device is completely removed from the vessel.
While the above-mentioned catheter can effectively cut and remove given portions of plaque from the interior of a vessel wall, the device has a number of limitations. More particularly, the P-SAC device involves forcing a full diameter housing through the plaque at a stenotic portion of a vessel. Further, the longitudinally disposed balloon must be relied upon to force the plaque into the aperture on the side of the housing so that a limited amount of material from one side of the plaque can be removed. Thus, this process is likely to result in significant tearing of the plaque and vessel wall (dissection) as is the case with some of the standard angioplasty techniques. Indeed, the resultant trauma to the vessel wall could result in a reactive cellular proliferative response commonly seen with standard balloon angioplasty which results in a high incidence of restenosis at the site of the original lesion.
It would be desirable to provide a cutter that can circumferentially cut or excise plaque material from the vessel walls so that repeated removal and reinsertion of the atherectomy catheter to cut the plaque from about the circumference of the vessel are not necessary. It would also be desirable to provide a device which can excise a maximum amount of plaque once it is adjacent a target stenotic lesion so that repeated insertion and guiding of the device into the coronary arteries is minimized.
Further, it would be desirable to provide a plaque-coring catheter which can excise a maximum amount of plaque while minimizing the likelihood of lacerating the vessel.